“Blackfish” star and former killer whale trainer John Hargrove has signed a book deal with Macmillan Publishing for his upcoming memoir, “Beneath the Surface.”

Hargrove (above), a former SeaWorld employee, will tell the extraordinary stories of the whales he worked with and came to love, his experiences in and out of the water, and his determination to advocate for this being the last generation of killer whales in captivity.

Hargrove previously spoke to TheWrap about “Blackfish,” director Gabriela Cowperthwaite’s documentary exploring — and showing — the harrowing effects captivity can have on an animal meant to live in the wild.

“It only focuses on a handful of events, but there were so many others. We just scratched the surface,” Hargrove said during the candid interview. “There’s so many incidents that we did not bring up in ‘Blackfish,’ that trainers nearly died and we didn’t even touch on those. So, I mean, they should be grateful that we only brought up what we brought up. If there was more time, it would have been a less-flattering picture for them, for sure.”

Since “Blackfish’s” debut, Hargrove has spent most of his time advocating on behalf of the killer whales by urging both California and NY state legislators to pass bills that would ban the captivity of killer whales for entertainment at SeaWorld.

“Beneath the Surface” is expected to hit bookshelves sometime during the spring in 2015.